Method and apparatus for multicasting with feedback information

Abstract

A method for multicasting a packet begins by providing a buffer for each of two user equipments (UEs) in communication with a base station. A determination is made whether there is a previously unsent packet at the base station. A second determination is made whether both UE buffers are non-empty. A non-empty buffer is flushed if there is no previously unsent packet and if one of the buffers is non-empty. A packet is selected to be transmitted if there is a previously unsent packet or if both buffers are non-empty. The buffers are updated based on feedback received from the UEs.

1. A method for multicasting a packet, comprising:
 providing a buffer at a base station for each of two user equipments (UEs) in communication with the base station, each buffer configured to store packets to be sent to the corresponding UE; 
 determining whether there is a new packet at the base station to be transmitted to a UE, wherein a new packet is a previously unsent packet; 
 determining whether both UE buffers are non-empty; 
 flushing a non-empty buffer on a condition that there is no new packet and on a condition that one of the buffers is non-empty; 
 selecting a packet to transmit on a condition that there is a new packet or on a condition that both buffers are non-empty, wherein a combined packet is selected on a condition that there is no packet that has been previously transmitted but not acknowledged by both UEs and on a condition that both buffers are non-empty, wherein a combined packet is an exclusive OR combination of a first packet in each buffer; and 
 updating the buffers based on feedback received from the UEs, wherein the updating includes removing a packet from a buffer on a condition that the UE acknowledges receipt of the packet. 
 
     
     
       2. The method according to  claim 1 , wherein the flushing includes:
 determining whether the buffer is empty; 
 transmitting a packet from the buffer on a condition that the buffer is non-empty; 
 updating the buffer based on feedback received from the UE, wherein the updating includes removing a packet from a buffer on a condition that the UE acknowledges receipt of the packet; and 
 repeating the flushing until the buffer is empty. 
 
     
     
       3. The method according to  claim 1 , wherein the selecting includes:
 transmitting a packet that has been previously transmitted but not acknowledged by both UEs. 
 
     
     
       4. The method according to  claim 1 , wherein the selecting includes:
 transmitting a new packet on a condition that there is no packet that has been previously transmitted but not acknowledged by both UEs and on a condition that one of the buffers is empty. 
 
     
     
       5. The method according to  claim 1 , wherein the selecting includes:
 examining a first packet in a non-empty buffer; 
 determining whether the first packet is a predetermined number of packets ahead of a most recently transmitted packet; and 
 transmitting the first packet on a condition that the first packet is the predetermined number of packets ahead of the most recently transmitted packet. 
 
     
     
       6. The method according to  claim 5 , wherein the predetermined number of packets ahead of the most recently transmitted packet corresponds to a maximum delay value. 
     
     
       7. The method according to  claim 1 , wherein the selecting includes transmitting a first packet in the buffer on a condition that the buffer has reached a predetermined buffer capacity. 
     
     
       8. A method for providing feedback in a multicast communication system, comprising:
 receiving a packet from a base station; 
 determining whether the received packet is a combined packet; 
 recovering individual packets from the combined packet, wherein the recovering includes performing an exclusive OR operation on the combined packet and a previously received packet, whereby a previously unsuccessfully received packet is recovered; and 
 providing feedback to the base station for any individual packet in the combined packet that was not previously successfully received. 
 
     
     
       9. A base station configured to multicast a packet, comprising:
 two buffers, one buffer for each of two user equipments (UEs) in communication with the base station; 
 a processor configured to:
 determine whether there is a new packet to be transmitted to a UE, wherein a new packet is a previously unsent packet; and 
 determine whether both buffers are non-empty; 
 
 a buffer flushing device configured to flush a non-empty buffer on a condition that there is no new packet and on a condition that one of the buffers is non-empty; 
 a packet selector configured to
 select a packet to transmit on a condition that there is a new packet or on a condition that both buffers are non-empty; 
 select a combined packet on a condition that there is no packet that has been previously transmitted but not acknowledged by both UEs and on a condition that both buffers are non-empty, wherein a combined packet is an exclusive OR combination of a first packet in each buffer; 
 
 a buffer updating device configured to:
 update the buffers based on feedback received from the UEs; and 
 remove a packet from a buffer on a condition that the packet has been acknowledged by the corresponding UE; and 
 
 a transceiver configured to transmit packets and to receive feedback information. 
 
     
     
       10. The base station according to  claim 9 , wherein said buffer flushing device is configured to:
 determine whether the buffer is empty; 
 select a packet from the buffer for transmission on a condition that the buffer is not empty; and 
 repeat flushing the buffer until the buffer is empty. 
 
     
     
       11. The base station according to  claim 9 , wherein said packet selector is configured to select a packet that has been previously transmitted but not acknowledged by both UEs. 
     
     
       12. The base station according to  claim 9 , wherein said packet selector is configured to select a new packet on a condition that there is no packet that has been previously transmitted but not acknowledged by both UEs and on a condition that one of said buffers is empty. 
     
     
       13. The base station according to  claim 9 , wherein said packet selector is configured to:
 examine a first packet in a non-empty buffer; 
 determine whether the first packet is a predetermined number of packets ahead of a most recently transmitted packet; and 
 select the first packet on a condition that the first packet is the predetermined number of packets ahead of the most recently transmitted packet. 
 
     
     
       14. The base station according to  claim 13 , wherein the predetermined number of packets ahead of the most recently transmitted packet corresponds to a maximum delay value. 
     
     
       15. The base station according to  claim 9 , wherein said packet selector is configured to select a first packet in the buffer on a condition that the buffer has reached a predetermined buffer capacity.